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Low-coherence interferometry
Published in Pablo Artal, Handbook of Visual Optics, 2017
LCI biometry achieves a very high precision, both for the axial eye length and the anterior segment. While sub-μm precision can be achieved for central corneal thickness (Drexler et al. 1997b), precision figures on the order of 5–10 μm were reported for the anterior chamber depth, lens thickness, vitreous length, and axial eye length. Table 3.2 compares precision results obtained by repeated LCI and ultrasound measurements in 85 cataract eyes (Drexler et al. 1998b). As can be seen, the precision of LCI is an order of magnitude (or more) better than that of ultrasound biometry. By eliminating residual accommodation using cycloplegia, the precision of anterior chamber depth and lens thickness measurements could be further improved to values below 2 μm in healthy volunteers (Drexler et al. 1997b). In addition to standard biometry, the high precision and resolution of LCI enabled detailed studies of, for example, anterior chamber depth and lens thickness changes during accommodation (Drexler et al. 1997a), eye elongation during accommodation in emmetropes and myopes (Drexler et al. 1998b), and the lens–capsule distance in pseudophakic eyes (Findl et al. 1998).
Measuring mental workload: ocular astigmatism aberration as a novel objective index
Published in Ergonomics, 2018
Raimundo Jiménez, David Cárdenas, Rosario González-Anera, José R. Jiménez, Jesús Vera
Wavefront aberrations were measured before mentally demanding tasks, just after 11 min of mental effort, after finishing the 33 min of the mental task, and after 10 min of passive recovery. Aberrometry was performed under mesopic conditions without any cycloplegia or mydriasis by the OPD Scan III (Nidek Inc., Tokyo, Japan). The OPD-Scan lll is a five-in-one true refractive work station combined with a topographer, wavefront aberrometer, keratometer, and pupillometer, for which the repeatability and accuracy have been determined in previous studies (Burakgazi et al. 2006). Combined wavefront aberrometry and corneal topography can differentiate between aberrations caused by the anterior cornea or by the internal ocular system. Total ocular aberrations are the result of corneal and internal ocular aberrations.
The changing scope of Optometry in New Zealand: historical perspectives, current practice and research advances
Published in Journal of the Royal Society of New Zealand, 2019
Joanna M. Black, Robert J. Jacobs, John R. Phillips, Monica L. Acosta
The future direction of clinical myopia control is likely to encompass several themes: all are in their infancy. A major theme, aimed at reducing the incidence of myopia in schoolchildren, will rely on inter-disciplinary development and implementation of future public health policies and standards, including public education, regarding children’s light exposure (Health and Safety at Work (General Risk and Workplace Management) Regulations 2016). Current evidence suggests that maintaining adequate light levels within school classrooms and also ensuring that children spend sufficient time outdoors during the day, will be the starting point for public health efforts to inhibit myopia development in children (Petty and Wilson 2018). Implementation of such programmes is beginning in parts of Asia, but necessary evidence regarding what constitutes adequate light levels and outdoor time is still lacking. A second theme within myopia control is to enable widespread implementation of clinical methods for reducing the rate of progression of myopia in those children who develop it. Almost all current evidence-based optical methods for correcting myopia rely on contact lenses, which have many limitations for use in children (increased risk of serious eye infection, difficulty in handling, limited ability to correct cylindrical error, high cost etc.) and are therefore not universally applicable. Spectacles are much more universally appropriate, but there is yet no longer-term evidence regarding efficacy. Atropine appears to be the most effective method for controlling myopia progression, but concentrations necessary for effective myopia control are also associated with significant unpleasant side effects of mydriasis and cycloplegia. This has led to the widespread adoption of ‘low-dose’ atropine. Low dose atropine is less effective and its true efficacy in terms of reducing abnormal eye elongation is debated. Therefore a potential future area for research in myopia control would appear to lie in the development of effective pharmacological agents with minimal side effects that might replace atropine.